<?php
/**
 * Zend Framework
 *
 * LICENSE
 *
 * This source file is subject to the new BSD license that is bundled
 * with this package in the file LICENSE.txt.
 * It is also available through the world-wide-web at this URL:
 * http://framework.zend.com/license/new-bsd
 * If you did not receive a copy of the license and are unable to
 * obtain it through the world-wide-web, please send an email
 * to license@zend.com so we can send you a copy immediately.
 *
 * @category   Zend
 * @package    Zend_Memory
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @version    $Id: Value.php 16971 2009-07-22 18:05:45Z mikaelkael $
 */


/**
 * String value object
 *
 * It's an OO string wrapper.
 * Used to intercept string updates.
 *
 * @package    Zend_Memory
 * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
 * @license    http://framework.zend.com/license/new-bsd     New BSD License
 * @todo       also implement Countable for PHP 5.1 but not yet to stay 5.0 compatible
 */
class Zend_Memory_Value implements ArrayAccess {
	/**
	 * Value
	 *
	 * @var string
	 */
	private $_value;

	/**
	 * Container
	 *
	 * @var Zend_Memory_Container_Interface
	 */
	private $_container;

	/**
	 * Boolean flag which signals to trace value modifications
	 *
	 * @var boolean
	 */
	private $_trace;


	/**
	 * Object constructor
	 *
	 * @param string $value
	 * @param Zend_Memory_Container_Movable $container
	 */
	public function __construct($value, Zend_Memory_Container_Movable $container)
	{
		$this->_container = $container;

		$this->_value = (string)$value;

		/**
		 * Object is marked as just modified by memory manager
		 * So we don't need to trace followed object modifications and
		 * object is processed (and marked as traced) when another
		 * memory object is modified.
		 *
		 * It reduces overall numberr of calls necessary to modification trace
		 */
		$this->_trace = false;
	}


	/**
	 * ArrayAccess interface method
	 * returns true if string offset exists
	 *
	 * @param integer $offset
	 * @return boolean
	 */
	public function offsetExists($offset)
	{
		return $offset >= 0  &&  $offset < strlen($this->_value);
	}

	/**
	 * ArrayAccess interface method
	 * Get character at $offset position
	 *
	 * @param integer $offset
	 * @return string
	 */
	public function offsetGet($offset)
	{
		return $this->_value[$offset];
	}

	/**
	 * ArrayAccess interface method
	 * Set character at $offset position
	 *
	 * @param integer $offset
	 * @param string $char
	 */
	public function offsetSet($offset, $char)
	{
		$this->_value[$offset] = $char;

		if ($this->_trace) {
			$this->_trace = false;
			$this->_container->processUpdate();
		}
	}

	/**
	 * ArrayAccess interface method
	 * Unset character at $offset position
	 *
	 * @param integer $offset
	 */
	public function offsetUnset($offset)
	{
		unset($this->_value[$offset]);

		if ($this->_trace) {
			$this->_trace = false;
			$this->_container->processUpdate();
		}
	}


	/**
	 * To string conversion
	 *
	 * @return string
	 */
	public function __toString()
	{
		return $this->_value;
	}


	/**
	 * Get string value reference
	 *
	 * _Must_ be used for value access before PHP v 5.2
	 * or _may_ be used for performance considerations
	 *
	 * @internal
	 * @return string
	 */
	public function &getRef()
	{
		return $this->_value;
	}

	/**
	 * Start modifications trace
	 *
	 * _Must_ be used for value access before PHP v 5.2
	 * or _may_ be used for performance considerations
	 *
	 * @internal
	 */
	public function startTrace()
	{
		$this->_trace = true;
	}
}
